The goal of this investigation is the description of the ultrastructural morphology and elucidation of the molecular pathogenesis of organic mercurial intoxication in the central nervous system. Previous studies have described a methyl mercury induced defect in cerebellar slice and synaptosome protein synthesis and respiration. Our immediate goal is an examination of the effects of methyl mercury in vivo and in vitro on cerebral slice and synaptosome RNA and DNA synthesis. The mitochondrion is involved in RNA and DNA synthesis and will allow for comparison of mitochondrial and non-mitochondrial protein synthesis following methyl mercury intoxication. The effects of methyl mercury in vitro on the morphology (size, shape, and volume) of isolated synaptosomes will be examined by electron microscopy. BIBLIOGRAPHIC REFERENCES: Verity, M., Cheung, M., and Latta, J.: Characterization of ouabain inhibition of synaptosome protein synthesis. Trans. Am. Soc. Neurochem., 8:1977. Cheung, M., Latta, J., and Verity, M.A.: Nucleoside incorporation into synaptosome fraction DNA and RNA: Effect of selective inhibitors. Trans. Am. Soc. Neurochem., 8:1977, in press.